The present invention provides a web development system. In a running state of a web application being developed, the development system generates or modifies a script code used to perform a predetermined function. The development system includes a script parser that parses the generated script code or the modified script code to correspondingly generate an object type which performs a new function, or to modify the object type which performs an existing function. The development system also includes an object manager that generates a new function object or modifies the existing function object according to the generated object type and organizes the invoking relationships between the new or modified function object and other objects, so as to generate or modify the predetermined function when the web application is operating.